Oscillating drive for doffer comb



March. 4, 1969 J. K. P. MACKIE OSCILLATING DRIVE FOR DOFFER COMB Sheet of 2 Filed April 24, 1967 March. 4, 1969 J. K. P. MACKIE OSCILLATING DRIVE FOR DOFFER COMB Sheet 2 of 2 Filed April 24, 1967 United States Patent O 3,430,296 OSCILLATING DRIVE FOR DOFFER COMB John K. P. Mackie, Belfast, Northern Ireland, assignor to James Mackie & Sons Limited, Belfast, Northern Ireland, a British company Filed Apr. 24, 1967, Ser. No. 633,095 Claims priority, application Great Britain, Apr. 29, 1966,

19,029/ 66 U.S. Cl. 19-106 13 Claims Int. Cl. D01g 15/46 ABSTRACT F THE DISCLOSURE It is sometimes necessary in the operation of a textile machine, to produce a rapid angular oscillation of a memyber about a longitudinal axis. One particular example of such a requirement is the operation of doifer combs for use with doing rollers on cards and other textile machines. These combs are carried by -arms projecting from a shaft mounted in front of the dotring roller and caused to oscillate so that the combs strip the fibrous material from the pins of the roller. The present invention will be described in terms of the operation of such a comb shaft but it will be understood that it is equally applicable to other forms of oscillatory mechanism used in textile machines. In particular the oscillatory member need not be a shaft.

The simplest manner of producing the necessary oscillation is by means of a crank secured to the shaft and driven by an eccentric turned at the required speed. This has several disadvantages, however, the most important of which is that the speed of reversal differs at the two ends of the stroke. As an alternative, therefore, proposals have been made to drive the shaft electromagnetically. F or this purpose the shaft is usually connected to a member similar to the rotor of an electric motor which is caused to oscillate by an oscillatory magnetic field. The connection of such a member to the moving comb shaft adds greatly to the reciprocating masses and thus the inertia loading. With such an arrangement the eliiciency of operation can be increased by providing torsional control for the shaft so as to form a resonant system having a natural frequency corresponding to the frequency of oscillation of the magnetic eld. Under these circumstances less power is required since it is merely a question of maintaining the shaft in a state of resonance and of adding further power corresponding to the work done by the doler comb or other equipment.

The torsional control may most simply be provided 'by a torsion bar and in the case of a comb shaft :which is normally hollow this bar may extend along the centre of the hollow shaft. The torsion bar needs to be anchored at one end and to be connected at the other end to the hollow shaft which is mounted to turn freely in bearings. By Ia suitable choice of the characteristics of the torsion bar and of the shaft assembly the mechanism as a whole can be caused to resonate at the required frequency. Other forms of torsional control are also possible and "Ice the dolfer comb may 4be mounted directly on the torsion bar.

According to the present invention -a shaft or other member mounted to form part of Ia resonant system is driven by mechanism producing repetitive mechanical impacts acting or re-acting on the surface of an element connected to or forming part of the member but radially displaced from its axis. By adjusting the frequency of these impacts to correspond with the resonant frequency of the system as a whole the mechanism is driven into a state of resonance and once this state has been achieved only a relatively small additional supply of power is necessary to maintain it.

By producing the impacts at the resonant frequency the shaft or other member immediately starts to oscillate at this frequency and the amplitude of movement rapidly builds up to its full operating value. This is in contrast to the result obtained with a direct mechanical drive eg. by an eccentric, where the amplitude of movement starts olf at its full value and the frequency increases from zero to its operating value. With a build-up of frequency this will pass through a critical value arising from the fact that the combination of the shaft and for example the combs is also capable of transverse oscillation lby bowing and the natural frequency of this mode of Oscillation is less than that corresponding to the torsional mode. When the frequency passes through this critical value the combs are caused to vibrate in a direction at right angles to the surface of the doifer roller. To avoid the risk of the combs striking the pins of the dolfer roller the clearance between the combs and the roller must be lmade relatively large. This reduces the eiciency of operation lbut cannot be avoided if the shaft has to be driven through the critical frequency. With a construction in accordance with the invention the clearance can be made as small as required because the shaft never has to pass through the critical frequency.

The term mechanical impacts is used to indicate that the energy of a moving mass is caused to act or react on the said surface of said element which is preferably formed as an arm extending laterally from the member. Most conveniently the mechanical impacts are produced by means of compressed air. Generally speaking, however, the use of the reaction of the impacts rather than the direct action is not so practicable and will not be further described.

When using compressed air to produce the impacts the energy is preferably used indirectly so as to control a striker which in its turn engages the arm extending from the shaft or other member. This striker consists most simply of a flexible diaphragm which is caused to vibrate by the application of pulses of compressed air at the required frequency. Provided the diaphragm is exible it need not -be elastic since the air pressure need not stretch the diaphragm but merely cause it to project into contact with the arm to produce the necessary impact. The striker then needs to be controlled by a spring so as to vibrate at a natural frequency equal to that of the shaft which is being driven.

Since the arm which is engaged by the striker is oscillating at a resonant frequency it executes a simple harmonic motion and its velocity at the end of its stroke is small. It is at this point that it then receives additional energy from each successive impact. Immediately after the impact the arm accelerates at a rate greater than the striker so that the striker is effectively left behind.

Since, moreover, the striker provides only a relatively small proportion of the total energy on each stroke Jthe amplitude of movement of the striker may be very much less than that of the arm. Stated differently, since in bringing about the mechanical impacts, the amplitude of movement of the striker is very much less than that of the arm,

theA movement of the striker may be referred to as an abrupt blow or as being of short duration and stroke. If compressed air is used as the source of power this means that only a relatively small volume of air corresponding to a short stroke of the diaphragm is required. It also means that the mean point about which the diaphragm oscillates must move outwardly as the amplitude of movement of the arm builds up after the start of operation.

As mentioned previously only a relatively small quantity of power is needed to maintain the shaft or other member in a state or resonance and when the mechanism is running without load this is all the power which is required. For example, a doler comb may be run up to speed before the remainder of the card is in operation so that initially no work needs to be done by the dotfer combs. As soon as the load comes on, that is to say, the combs begin to strip libres from the dofiing roller the power required immediately rises and may tend to vary according to the quantity of libres to be doed at any time. Moreover some libres produce a greater load on the combs than others and the effect of a heavy load inevitably tends to slow down the oscillatory movement. This may then have the effect of driving the mechanism out of its state of resonance thus leading to the possibility of stalling. On the other hand if the power input is adjusted to suit an average load and this load suddenly becomes very much less, the amplitude of oscillation may exceed safe limits.

In order to overcome this diiculty the magnitude of the mechanical impacts may be controlled in accordance with the amplitude of oscillation in such a way as to maintain this amplitude substantially constant. In other words, if the load increases and the amplitude decreases correspondingly, the magnitude of the mechanical impacts is automatically increased so as to counteract this effect. Similiarly if the amplitude tends to approach its upper limits the power input, and hence the magnitude of the mechanical impacts, is reduced accordingly. When compressed air is used as the source of power the magnitude of the impacts is controlled quite simply by adjusting the pressure of the compressed air. On the other hand if the power is applied mechanically as described above a similar eect may be achieved by adjusting the rigidity of the lobe or lobes of the cam referred to above. For example, each lobe may be iniata-ble so that increase of the air pressure to each lobe adjusts its rigidity and hence its impact force.

The pressure of the compressed air, whether it is to be used as the source of power or, for example, merely for iniiating the lobe or lobes of a cam providing the mechanical impacts, may conveniently be controlled by means of a pneumatic circuit including a pressure regulator in which a throttling valve is acted on by a subsidiary air pressure which is itself controlled in accordance with the ampliutde of oscillation. 'Ihis subsidiary air pressure needs to be controlled so as to increase with a decrease of amplitude thus opening the valve further to increase the pressure of the main compressed air supply. An increase of amplitude then has the opposite effect, serving to decrease the subsidiary air pressure and hence to decrease the pressure of the main compressed air supply. The pressure regulator may be so constructed that the main air pressure tends to move the valve towards its closed position while the subsidiary air pressure acts on a diaphragm in conjunction with a spring to tend to open the valve.

The subsidiary air pressure itself is preferably adjusted by an interrupted air flow signal device controlled by an interrupter oscillating with the shaft. The signal device may, for example, control a pneumatic relay which in its turn controls the subsidiary air pressure. Other forms of control are also possible such as optical systems, ultrasonic systems and so forth. In each case the system reponds to the amplitude of the oscillation to have ascorresponding controlling eifect on the main air pressure.

A dofer comb assembly for use with a dofiing roller and including an oscillatory mechanism in accordance with the invention will now be described in more detail by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of the mechanical assembly with part exploded and a pneumatic control circuit shown in cross section;

FIGURE lA is a sectional view of the exploded portion of FIGURE l;

FIGURE 2 is a sectional view with the central portion broken away of the oscillatory shaft and its associated components; and,

FIGURES 3 to 5 are end views of the shaft seen from the left of FIGURE 2 showing different positions in the oscillatory stroke.

Turning first to FIGURE 1 a hollow shaft 1 carries a doffer comb 2 by means of radially extending arms 3. The shaft is caused to oscillate about its axis to produce a vertical oscillatory movement of the comb 2 which produces the necessary stripping action of the librous material when the assembly as a whole is mounted adjacent a doing roller. The construction of the hollow shaft is seen in more deail in FIGURE 2 and at the lefthand end it is fixed to a solid axle portion 5 turning in a ball bearing 6 in part of a fixed framework 7. The axle portion 5 is also fixed to a torsion bar 9 which extends within the hollow interior of the shaft 1 4and is anchored at its opposite end to a xed bar 12. The bar 12 in its turn is held by means of bolts 13 within a further part 14 of a ixed framework. The bar 12 also supports a second smaller ball bearing 15 on which the right-hand end of the shaft 1 can turn. The shaft 1 is therefore freely mounted at its two ends by means of the bearings 6 and 15 but its oscillatory movement is restrained as a result of torsion of the torsion bar 9.

The shaft 1 together with the torsion bar 9 forms a resonant system and by suitable choice of the characteristics of the components the natural frequency may be such as to give the required rate of oscillation of the comb 2. As so far described this assembly is of a generally known type. The invention is concerned with the driving mechanism to the assembly which will now be described in more detail.

As best seen in FIGURES 3 to 5 the axle portion 5 has two laterally extending arms 20 each formed with an anvil portion 21 for receiving mechanical impacts from a diaphragm 22 which is caused to vibrate by means of compressed air supplied to its interior. As seen in plan view the transverse arms 20 extend at an angle to the axis of the shaft 1 so that the anvils 21 lie beyond the end of the axle portion 5 as can be seen in the perspective view of FIGURE 1. The diaphragms 22 are mounted in an assembly comprising a pair of plates 23 held together by screws 24 and including internal passages for the compressed air supply to the two diaphragms 22. The inlets for the compressed air to this assembly are shown in FIGURE 1 as 26 and these communicate with a manifold 27 which is shown exploded in FIGURE 1A for clarity of illustration. This manifold 27 forms part of a rotary valve assembly indicated generally as 28 which is driven by a belt (not shown) passing around a pulley 29. Compressed air enters the valve assembly at 32, passes to the two diaphragms 22 and is then exhausted again at 33. The air is controlled by a rotor 35 seen in FIGURE 1A which is driven by the pulley 29 and includes two cut-away portions 36. For one angular position of the rotor 35 one of the cutaway portions 36 connects the inlet 32 with a port 37 leading to the interior of the manifold 27 and thence to the two diaphragms 22. As the rotor 35 turns from this position the inlet y32 is first closed and immediately afterwards the outlet 33 is opened to exhaust air from the diaphragms. A further stage of rotation brings the second cut-away portion into connection with the inlet 32 so that the diaphragms are caused to carry out two complete cycles of vibration for each revolution of the rotor 35.

FIGURE 3 shows the symmetrical position of the oscillatory assembly. On receipt of a pulse of compressed air from the rotary valve 28l the diaphrams 22 are distended into the position shown in this iigure to produce a mechanical impact on the two anvils 21 thus turning the shaft 1 in an anticlockwise direction. On starting up the amplitude will be small and the anvils 21 will generally not move out of contact with the diaphragms. The pulley 29, however, is driven at a speed corresponding to the resonant frequency of the assembly which is thus driven into a state of resonance and the amplitude builds up rapidly. FIGURE 4 shows the position of the assembly in which the shaft 1 has turned through the normal full stroke in an anticlockwise direction. Here it will be seen that although the diaphragms are not distended beyond the position of FIGURE 3 the anvils 21 have moved clear of them.

FIGURE 5 shows the assembly at the end of its normal stroke in the opposite direction and it will be seen that since the two diaphragms are connected to exhaust they are able to collapse and allow the anvils 21 to move beyond the normal rest position of the diaphragms. It will thus be understood that when the mechanism is rst started the frequency is at its full operating value, that is to say, the resonant frequency of the system and the amplitude which starts olf from zero rapidly builds up to its full operating value. Since the frequency does not have to pass through the critical value described earlier the danger of harmful extraneous vibration is avoided. As long as there is no load on the comb 2 the amount of power required to keep the system oscillating as just described is relataively small but as soon as the system is loaded there is a tendency for the amplitude of oscillation to be reduced and this will, of course, depend both on the weight and nature of the libres as already described. In order to maintain the amplitude at its normal value and thus to maintain the eticiency of the stripping action the power input is automatically adjusted by means of a pneumatic control circuit indicated generally as 40.

The main component of this circuit is a pressure regulator 41 to which compressed air is supplied at 42 and which supplies air at 43 to the inlet 32 of the rotary valve 2. This regulator includes a throttling valve 45 which tends to be held against its seating 46 by means of the pressure of the incoming air assisted by a light spring 47 and which is moved away from its seating so as to provide an adjustable throttling action by means of a compression spring 48 controlled by an adjusting screw 50. In this way an overriding manual adjustment can be applied to the air pressure supplied to the valve 28. superimposed on this manual control is an automatic control which is dependent on the amplitude of oscillation of the shaft 1. For this purpose the axle portion 5 carries an interrupter in the form of a blade 52 which in the position of FIGURE 3 is located between an air jet 53 and a corresponding opening 54, best seen in FIGURE 2. AS long as the blade 52 obstructs the jet 53 no air pressure is transmitted to the opening 54 but when the blade 52 moves to the position of FIGURE 5 a brief pulse of compressed air is passed to the opening 54. Accordingly when the shaft 1 is oscillating with its normal maximum amplitude the opening 54 will receive one pulse of air per cycle, If for any reason the amplitude increases the duration of the pulses of air will also increase. Similarly if the amplitude of oscillation decreases the duration of the pulses will also decrease until a point is reached in which the air is cut oi altogether.

The combination of the blade S2 together with the jet 53 and the opening 54 thus constitutes an interrupted air ow signal device. Compressed air is supplied to this by way of an air line 55 which passes to a double-ported restrictor 56 having a pair of tapered restricting screws 57 and 58 which control the air pressures to an air relay 60 and to the air jet 53 respectively. In the position shown air enters the relay 60 by way of a line 61, passing into a lower chamber 62 and thence via a line `63 to an upper chamber 64 in the regulator 41. This pressure acts on the upper side of a diaphragm 65 and assists the action of the spring 48 in opening the throttling valve 45. Stability is achieved by the provision of a bleed 68 through which air pressure is supplied to the lower side of the diaphragm 65 so that any variations in the main supply pressure are automatically cancelled since they act equally on both sides of this diaphragm.

Air pressure supplied from the jet 53 to the opening 54 passes along a line 70 to an upper chamber 71 in the relay 60 where it acts on the upper surface of a diaphragm 72. This diaphragm cooperates with an orice 73 and controls the ow of air through this orifice from a central chamber 74. Air passes to this chamber from a bleed 75 connecting the lower chamber 62 and the central chamber 74, In the position shown air passes through the bleed 75, through the orifice 73 and thence to atmosphere through an outlet 76. An increase in the pressure applied along the line 70 to the upper side of the diaphragm 72 tends to restrict and ultimately to close the orifice 73 thus causing pressure to build up in the central chamber 74. This acts on the upper surface of a diaphragm 78 moving this downwardly and thus causing a valve 80 to move downwardly away from its seating so allowing air from the lower chamber 62 to flow to atmosphere through an outlet 81. Air in the space below the diaphragm 78 escapes through a slight clearance round the stem of the valve 80. This reduces the air pressure supplied to the upper chamber 64 in the regulator 41, thus tending to close the throttling valve 45 and so to reduce the main air supply pressure.

The action just described results from an increase in the pressure supplied along the line 70 by the air signalling device which in its turn results from an increase in the amplitude of oscillation. In other words an increase in the amplitude of oscillation leads to a decrease in the main air supply thus reducing the magnitude of the impacts applied by the diaphragms 22 and hence tending to reduce the amplitude of oscillation. Under normal operating conditions a balance is achieved in which the value of the pressure as controlled by the air signalling device regulates the main air pressure to maintain the amplitude at its existing value. An increase in amplitude tends to open the valve 80 further so as to reduce the air pressure in the chamber 64 in the regulator 41 while a decrease in amplitude has the opposite effect, tending to close the valve 80 and thus to increase the pressure in the chamber 64 and to increase the main operating air pressure. In other words the system as a whole is selfregulating and the amplitude of oscillation of the shaft 1 and hence of the comb 2 will be maintained substantially constant over a wide range of operating loads,

I claim:

1. An oscillatory mechanism for a textile machine comprising a shaft supporting a doing comb and mounted for angular movement about a longitudinal axis, torsional control means connected to said shaft and constituting a resonant system, pneumatically operated drive means for producing repetitive mechanical impacts upon said torsional control means to produce oscillation of said resonant system and means responsive t0 the amplitude of said oscillation for regulating the air supply pressure of said driving mechanism so as to maintain said amplitude substantially constant.

2. Mechanism according to claim 1 having a pneumatic control circuit including a pressure regulator, said pressure regulator including a throttling valve, means controlling said valve in accordance with a subsidiary air pressure and means for adjusting said subsidiary air pressure in accordance with said amplitude.

3. Mechanism according to claim 2 including a spring urging said valve towards an open position against said air supply pressure, and a diaphragm acted on by said subsiliary air pressure to assist said spring.

4. Mechanism according to claim 2, including an interrupter oscillating with the shaft and an interrupted air ow signal device controlled by said interrupter and operative to adjust said subsidiary air pressure. v

5. In a doffer comb assembly for a textile machine comprising a doer comb, a shaft supporting said dotfer comb for oscillatory movement about an axis, and torsion means mounting said shaft to turn under torsional control and constituting a resonant system, the improvement comprising, at least one arm operatively connected to said shaft for movement therewith about said axis and extending laterally from said axis, and drive means for imparting to said at least one arm repeated mechanical impacts to impart oscillatory movement to the shaft such that the duration of said impacts are short relative to the duration of the amplitude of the said oscillatory movement of the shaft.

6. The invention of claim 5 wherein the drive means includes means for imparting said mechanical impacts of short duration and stroke to the said at least one arm at those moments when the shaft is changing direction in its said oscillatory movement about said axis.

7. The invention of claim 5 wherein said drive means includes means for imparting said mechanical impacts of short duration and stroke to said at least one arm to maintain oscillatory motion of said shaft at a frequency corresponding to the resonant frequency of said resonant system.

8. The invention of claim 5 wherein said drive means includes pneumatic means for producing said mechanical impacts.

9. The invention according to claim 8 wherein said drive means includes a striker controlled by said pneumatic means and which engages said at least one laterally extending arm.

10. The invention according to claim 5 in which said drive means comprises a flexible diaphragm and means for applying pulses of compressed air to said diaphragm, whereby said diaphragm produces said repetitive impacts on said arm.

11. The invention according to claim 10 wherein said assembly includes a pair of said laterally extending arms and said drive means includes a pair of diaphragms acting on said two arms and a single rotary valve member supplying compressed air to both diaphragms,

12. Apparatus according to claim 5 including means for controlling the magnitude of said mechanical impacts in accordance with the amplitude o f oscillation of said shaft in such a way as to maintain said amplitude substantially constant.

13. The invention of claim 5 including two laterally extending arms operatively connected to said shaft.

References Cited UNITED STATES PATENTS 2,604,669 7/1952 smith 19-106 FOREIGN PATENTS 5,483 of 1896 Great Britain. 477,650 1/1953 na1y. 149,995 9/1961 U.s.s.R.

DORSEY NEWTON, Primary Examiner. 

